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Light Baryon Spectroscopy – Recent Results. R. Beck HISKP, University Bonn IWHSS, 16. – 18.April 2012 , Lisbon. Introduction. Recent Results from ELSA, JLab and MAMI:. Narrow structure. Summary and Outlook. supported by the DFG within the SFB/TR16. Introduction.

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Light Baryon Spectroscopy – Recent Results

R. Beck

HISKP, University Bonn

IWHSS, 16. – 18.April 2012 , Lisbon

Introduction

Recent Results from ELSA, JLab and MAMI:

Narrow structure

Summary and Outlook

supported by the DFG within the SFB/TR16


Introduction

PDG 2010: Status on nucleon resonances

only 7N*and 5D*

established in the region 1400 MeV < W < 2000 MeV

L. Tiator

Energy pattern for the dominant states

Various nucleon models predict many more states

weak coupling to pN final state

Constituent Quark Models

insufficient data base

Dynamical Models

Lattice QCD


Introduction

talk yesterday by M. Peardon


Experimental program for N*

Common effort at ELSA, JLab and MAMI,

Precision data for different final states (pp0, np+, ph , K+L, pp0p0....)

Polarization experiments (beam, target and recoil)

“complete data base”

To constrain PWA -> unique PWA solution

g + p -> p + p- + p+

g +p -> p + p0 + p0

g +p -> p + p0

g +p -> K+ + L

g +p -> p + h


Problem with a unique PWA solution

8 well chosen observable have to be measured to determine the production amplitudes (F1,F2,F3 and F4)

p- threshold until D+(1232)- region

additional constraints:

(a) s- and p- wave approximation

(b) Fermi- Watson theorem

same I, J in the final state

same scattering phase dIJ

two observable sufficient for “complete data base”

differential cross section : ds/dW

beam asymmetry : S

above pp- threshold

Fermi- Watson theorem not valid any more

More observable needed to get a unique partial wave solution



Resonance parameter for the P33(1232)

O. Hanstein, D. Drechsel, and L. Tiator Phys. Lett. B 385, 45 (1996)

R.B. and H.P. Krahn Phys. Rev. Lett. 78, 606 (1997)

R.B. and H.P. Krahn Phys. Rev. C61, 035204 (2000)


Problem with a unique PWA solution

8 well chosen observable have to be measured to determine the production amplitudes (F1,F2,F3 and F4)

p- threshold until D+(1232)- region

additional constraints:

(a) s- and p- wave approximation

(b) Fermi- Watson theorem

same I, J in the final state

same scattering phase dIJ

two observable sufficient for “complete data base”

differential cross section : ds/dW

beam asymmetry : S

above pp- threshold

Fermi- Watson theorem not valid any more

More observable needed to get a unique partial wave solution


Problem with a unique PWA solution

V. Crede, O. Bartolomy et al.,

PRL 94 (2005) 012004,

EPJ A33 (2007) 133

Meson photoproduction

Photon helicity couplings: A1/2 und A3/2

BnGa partial wave analysis:

strong P13(1720) contribution

S11(1535) : A1/2 (S11(1535)) only

D13(1520) : A1/2 (D13(1520)) and A3/2(D13(1520))

Total cross section:

stot ~ |A1/2(S11)|2 + |A1/2(P13)|2 + |A3/2(P13)|2 + …..

P13(1720) : A1/2 (P13(1720)) and A3/2(P13(1720))


η-MAID

D15(1675)

Eγ=1250 MeV

D13(1520)

Σ

D13(1520)

BnGa PWA

P13(1720)

Θcm

Problem with a unique PWA solution

D. Elsner et al., EPJ A33 (2007) 147

Beam asymmetry: S

P11(1710)

Higher sensitivity because of interference

between different resonance contributions

S~ A1/2(S11) * A1/2(P13)+ …..

BnGa partial wave analysis:

strong P13(1720) contribution

MAID partial wave analysis:

D15(1675) and P11(1710) contribution

More observable needed to get

a unique partial wave solution


Observables in Meson Photoproduction

data only for:

data needed for:

Differential cross section:

s

Target asymmetry:

T

Beam asymmetry:

S

Recoil polarization:

P

Double polarization:

E

Double polarization:

G

Sensitive to:

Sensitive to:

ELSA, JLAB, MAMI : polarized photons, polarized targets and 4p acceptance


Today 17.4. 60th birthday of Fritz Klein

electron accelerator at the University of Bonn

W. Hillert, F. Klein

BGO-OD


Experiments at ELSA

  • Crystal Barrel Set-Up

  • BGO-OD Set-Up



Crystal Barrel Set Up at ELSA

  • Crystal Barrel detector

  • 1230 CsI crystals

  • Inner-detector

  • cylinder of 513 scintillating fibers

  • forward detector (FWPlug)

  • 90 CsI crystals with PM’s, 120-300

  • forward detector (MiniTAPS)

  • 216 BaF2 , 10-120

Close to 4p coverage


Polarized Photons

Linearly polarized photons:

- coherent bremsstrahlung

- diamond radiator

Circularly polarized photons:

- longitudinally polarized electrons

- helicity transfer to photon

Linearly polarized photons

Circularly polarized photons

high polarization at low photon energies

high polarization at high photon energies

ELSA, JLAB and MAMI


Butanol (C4H9OH)

Polarized Target

„Frozen Spin Target“

Horizontal cryostat with integrated

solenoid to freeze up the spin

Target: Butanol (C4H9OH)

Polarization: DNP at high B-field (2.5 T)

„freeze“ up the spin (0.4 T)

relaxation time T~500h

„transversely polarized Target“

„longitudinally polarized Target“

ELSA, JLAB and MAMI


Polarized Target at ELSA

Running time over 2500 hours in year 2008

over 2200 hours in year 2009

over 1500 hours in year 2010

over 1800 hours in year 2011

High. polarization P+ = 83.4 %

P- = - 80.9 %

fast build-up

Pol.-time 06h10min

horizontal cryostat

in experimental area

data taking

Bonn: H. Dutz, S. Goertz

Bochum: W. Meyer, G. Reicherz


Polarized Target at MAMI

Polarized Target running since beginning 2010


Polarized Target at JLAB

Polarized Target running since beginning 2007



P33 (1232)

F15 (1680)

S11 (1535)

Helicity dependent cross section for pp0

reaction:

circularly polarized photons

longitudinally polarized proton

count rate difference

acceptance correction

N1/2 - N3/2

with acceptance

correction

+ …

Crystal Barrel at ELSA (M. Gottschall, J. Müller)


Helicity dependent cross section for pp0

reaction:

Angular distributions sensitive to interference between resonances

Crystal Barrel at ELSA (M. Gottschall, J. Müller)

N1/2 - N3/2

E~

N1/2 + N3/2

partial wave analysis

prediction

__BnGa

__ SAID

__ MAID


S11 (1535)

F15 (1680)

E-Asymmetry for pp0 (ELSA Results)

Crystal Barrel at ELSA (M. Gottschall, J. Müller)

SAID: blue line

MAID: black line

BnGa: red line

PWA predictions

fail already

in 2. resonance region


S11 (1535)

P11 (1710)

P13 (1720)

Helicity dependent cross section for ph

reaction:

circularly polarized photons

longitudinally polarized proton

Crystal Barrel at ELSA (J. Müller)

N1/2 - N3/2

no acceptance

correction


η-MAID

D15(1675)

Eγ=1250 MeV

D13(1520)

Σ

D13(1520)

BnGa PWA

P13(1720)

Θcm

Problem with a unique PWA solution

D. Elsner et al., EPJ A33 (2007) 147

Beam asymmetry: S

P11(1710)

Higher sensitivity because of interference

between different resonance contributions

S~ A1/2(S11) * A1/2(P13)+ …..

BnGa partial wave analysis:

strong P13(1720) contribution

MAID partial wave analysis:

D15(1675) and P11(1710) contribution

More observable needed to get

a unique partial wave solution


S11 (1535)

P11 (1710)

P13 (1720)

Helicity dependent cross section for ph

reaction:

circularly polarized photons

longitudinally polarized proton

BnGa

BnGaCur


G-Asymmetry for pp0 (ELSA Results)


G-Asymmetry for pp0 (ELSA Results)

Crystal Barrel at ELSA (A. Thiel to be published)

SAID: red dashed

MAID: bluedotted

BnGa: black line

PWA predictions

fail already

in 2. resonance region


G-Asymmetry for pp0 (ELSA Results)

  • Below 1 GeV the discrepancies

  • can be traced back to the

  • E0+ and E2- multipoles

  • s- and d-wave contributions

  • E0+ multipole

  • S11(1535), S11(1650) and S31(1620)

  • E2- multipole

  • D13(1520) and D33 (1700)


E0+ and E2-Multipoles

  • E0+ multipole

  • S11(1535), S11(1650) and S31(1620)

  • E2- multipole

  • D13(1520) and D33 (1700)

SAID: blue

MAID: black

BnGa: red line


D13 partial wave

  • E2- multipole contribution from D13 and D33 partial waves

  • D13(1520)- resonance in D13 partial wave

SAID: blue

MAID: black

BnGa: red line


S11 partial wave

SAID: blue

  • E0+ multipole contribution from S11- and S31- partial waves

  • S11(1535)- and S11(1650)- resonances in S11-partial wave

MAID: black

BnGa: red line


E-Asymmetry for np+ (JLaB Results)

Preliminary results CLAS at JLAB(M. Dugger)


E-Asymmetry for np+ (JLaB Results)

Preliminary results CLAS at JLAB (M. Dugger)


Polarization Observables with trans. pol. Target

Circularly polarized photons

-> double polarization asymmetry F

Transversely polarized protons

Linearly polarized photons

-> double polarization asymmetry Hand P

Transversely polarized protons

-> in addition Beam asymmetry Sand

Target asymmetry T


F-Asymmetry for pp0 (MAMI Results)

Preliminary results Crystal Ball at MAMI(H.J. Arends, M. Ostrick)


Beam Asymmetry S for pp0 (ELSA Results)

Crystal Barrel at ELSA (A, Thiel, J. Hartmann)


Target Asymmetry T for pp0 (ELSA Results)

Crystal Barrel at ELSA (J. Hartmann)


Target Asymmetry T for pp0 (ELSA Results)

Crystal Barrel at ELSA (J. Hartmann)


Recoil Polarization P for pp0 (ELSA Results)

Crystal Barrel at ELSA (J. Hartmann)


Double Polarization Asymmetry H for pp0

Crystal Barrel at ELSA (J. Hartmann)



First Interpretation of Asymmetry

black line L <= 2 Fit and red line L <= 3 Fit


First Interpretation of Asymmetry

L <= 2 Fit

truncated partial wave analysis




Target Asymmetry T for ph(ELSA Results)


Target Asymmetry T for ph(ELSA Results)



Electromagnetic excitation off the neutron

Crystal Barrel at ELSA result

quasifree h photoprodruction:

Narrow structure in nh - final state

Publication:

I. Jaegle, B. Krusche, …

accepted by EPJA


Comparison Narrow Structure

Effect of photo-excitation of D15(1675) ?

Coupled channel effect of S11(1535) and P11(1710) ?

Interference effect of S11(1535) and S11(1650) ?

New narrow state with stronger photo-coupling to the neutron ?

-> polarization observables needed !!


Status on Meson Photoproduction Data Base

Crystal Barrel

at ELSA

Nearly complete

data base

CLAS

at JLAB

Complete data base

Crystal Ball

at MAMI

Only a few

experiments


Summary

First round of double polarization experiments

at ELSA, JLab and MAMI finished

Preliminary results for the polarization observable

T, P, G, E and H

Model independent partial wave analysis has started

- polarization observables are essential

- different final states are essential

New data will determine nucleon excitation spectrum


World Data Base

reaction:

Beam asymmetry S

Differential cross section

First round of double polarization

experiments with CB at ELSA:

Energy range for G: 600- 1300 MeV

Energy range for E: 500- 2100 MeV

Asymmetry E

Asymmetry G

Future plans for CB at ELSA:

Extend energy range to 3 GeV

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

Transversally polarized target

Installed and first data taken

Measurements on the neutron

polarized deuteron target





Introduction

3.2 GeV photon beam at ELSA used to study meson photoproduction

- study the nucleon resonance spectrum

Breit Wigner Resonances

Total Photon Absorption Cross Section

Spectroscopic Notation

Isospin

Spin


S-Asymmetry for pp0 (JLab Results)


S-Asymmetry for pp0 and np+ (JLab Results)


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